 |
| A detail of a quarried face |
Arriving at Jawbone Hill from Grenoside, I immediately encountered the Birley Stone, which was first mentioned in 1161 and was probably originally a way marker on the route from Ecclesfield to Bradfield, via Oughtibridge.
 |
| The Birley Stone |
Taking the path that runs south along the escarpment, I soon encountered the first of many small outcrops of Greenmoor Rock, which here forms thin irregular beds that have been quarried in several places to build the dry stone boundary wall.
 |
| Greenmoor Rock foundations to a dry stone field boundary wall |
The characteristics of the formation here are very similar to those seen further to the north at Hunshelf Bank and Don Hill Height, contrasting with the more massive sandstone at Green Moor which was quarried extensively to produce first class paving stone.
 |
| A detail of thin and irregularly bedded Greenmoor Rock |
Although I had obtained samples of the Greenmoor Rock from various other outcrops in Sheffield, this formation is extremely variable and is often composed with finer grained mudstone, which was once exploited by several large brickworks.
 |
| A specimen of Greenmoor Rock |
The sample I obtained with my Estwing hammer is muddy brown in colour and very fine grained, with a considerable proportion of degraded iron bearing minerals, which add to its colour, and very occasional tiny flakes of muscovite mica.
 |
| A delf in the Greenmoor Rock |
Continuing along the path, I encountered a number of small delfs that have been cut into the rock for building the dry stone walls, where more irregularly bedded flaggy sandstone is seen. The exposures are very discontinuous and, sometimes, the Greenmoor Rock is laid down as finer grained beds, which exhibit fine cross-lamination.
 |
| Ripples in the Greenmoor Rock |
I didn’t deviate from the well worn path along the escarpment but, as with the Pennine Lower Coal Measures Formation strata in many other parts of Sheffield, the lower slopes nearer to the River Don were once mined for coal and ganister using adits dug into the hillside.
 |
| A view south along the escarpment |
At one place, I followed the public footpath that runs at right angles across the field to Skew Hill, where I stopped briefly to look at the very gentle dip slope of the Greenmoor Rock and an escarpment in the distance, which is formed by the Grenoside Sandstone.
 |
| A panoramic view showing scarp and dip slopes |
In a few places, there are small outcrops adjacent to or along the path, where the bedding planes exhibit good examples of ripples. These are probably not the result of quarrying, which appears to be confined to the uppermost section of the Greenmoor Rock.
 |
| An exposure of Greenmoor Rock along the path |
Approaching the hamlet of Birley Edge, there is a more substantial rock face, which in one place has a series of drill holes that are a common site in quarries where blocks of building stone has been extracted by using plugs and feathers; however, there is no quarry marked here on any of the old Ordnance Survey maps that I have seen.
 |
| A section of Greenmoor Rock with drill holes |
On the day, the Don Valley was shrouded in haze, which obscured the views to Worrall, Wadsley and landmarks in the city centre but, although less than 1 km from the Birley Stone to Birley Edge, it was one of the most interesting parts of rural Sheffield that I had visited for a long time.
 |
| The walk from the Birley Stone to Birley Edge |
No comments:
Post a Comment